Systems and methods for controlling a conveyor in a mining system

ABSTRACT

Systems and methods for controlling a conveyor in a mining system. The conveyor includes a sprocket, a chain, a hydraulic cylinder, one or more sensors, and a controller. In one implementation, the method includes sensing a characteristic associated with the conveyor, generating a signal based on the characteristic, determining a tension associated with the chain based on the signal, determining an amount of chain stretch based on the tension, and modifying a position of the hydraulic cylinder based on the amount of chain stretch.

RELATED APPLICATIONS

This application claims the benefit of prior-filed, co-pending U.S.Provisional Patent Application No. 61/510,850, filed Jul. 22, 2011, theentire content of which is hereby incorporated by reference. Thisapplication also claims the benefit of prior-filed, co-pending U.S.Provisional Patent Application No. 61/510,839, filed Jul. 22, 2011, theentire content of which is also hereby incorporated by reference.

FIELD

This invention relates to the control of a conveyor, such as an armoredface conveyor (“AFC”), or a beam stage loader (“BSL”).

SUMMARY

Longwall mining systems include, among other things, an AFC or BSL totransport a mined material (e.g., coal) from an area where the materialis being mined to an area for processing (e.g., crushing, storage, etc.)AFCs include, for example, a first sprocket and a second sprocket aroundwhich a chain is provided. The chain is driven by one or more motors(e.g., a maingate motor, a tailgate motor, etc.), and the movement ofthe chain around the sprockets causes a conveyor to transport the minedmaterial.

Conventional AFCs that include an extendable return end frame usepre-tensioning techniques to increase chain tension around the sprocketsand avoid a slack chain or zero tension condition. The pre-tensioningtechniques include, for example, using a hydraulic cylinder to push thefirst sprocket away from the second sprocket. Packets or spacers arethen manually inserted near the sprocket to maintain the highpre-tension in the chain.

Pre-tensioning the chain as described above has a variety of drawbacks.For example, achieving and maintaining high pre-tension on the chain(e.g., 30-40 tons) increases the strain and wear of the chain, thesprockets, etc. Additionally, as the mined material is loaded onto theAFC, the tension of the chain further increases. As such, a chain thatis already experiencing strain as a result of the high pre-tensioningexperiences further increased strain as the mined material is loadedonto the conveyor.

Accordingly, the invention may generally provide, among other things,systems and methods for controlling an AFC to automatically controlchain tension by altering a sprocket position with a hydraulic cylinder.The invention may be used in conjunction with, for example, an AFC inwhich a first end of the AFC is fixed and a second end of the AFC isextendable. For such AFCs, the tension in the chain varies along thelength of the conveyor, and zero tension or slack chain conditionsshould be avoided in order to maximize the reliability of the AFC. Assuch, one construction of the system includes an AFC having anextendable return end frame, a first sprocket, a second sprocket, one ormore hydraulic cylinders, one or more chains, and a controller. At leastone of the first sprocket and the second sprocket include a drivemechanism (e.g., a motor and a motor controller). The drive mechanismturns the associated first sprocket and second sprocket to transport amined material from a first location to a second location, and thecontroller uses a measured electrical characteristic associated with theAFC to automatically control the position of the one or more hydrauliccylinders or sprockets.

For example, the controller utilizes a stored relationship between anelectrical characteristic of the one or more motors and a position ofthe one or more hydraulic cylinders, a position of the first or secondsprocket, a tension of the one or more chains, an amount of minedmaterial loaded on the conveyor, etc. Based on the electricalcharacteristic, the one or more hydraulic cylinders are controlled toincrease or decrease a distance between the first sprocket and thesecond sprocket to account for the stretching of the one or more chainsthat occurs when the mined material is loaded on the conveyor. Althoughpre-tensioning is still used, the amount of pre-tensioning required canbe reduced from approximately 30-40 tons to approximately fewer than 10tons (e.g., 5-6 tons) by dynamically modifying the position of, forexample, the one or more hydraulic cylinders based on the electricalcharacteristic. The reduction in the required amount of pre-tensioningreduces the amount of strain and wear on the components of the system.In another construction, the controller receives a direct measurement ofthe tension of the one or more chains from a chain tension sensor. Basedon the measured chain tension, the one or more hydraulic cylinders arecontrolled to increase or decrease the distance between the firstsprocket and the second sprocket to account for the stretching of theone or more chains.

In one implementation, the invention may provide a method of controllinga position of a hydraulic cylinder in an armored face conveyor. Thearmored face conveyor includes a sprocket, a chain, the hydrauliccylinder, and a controller. The method may generally include sensing anelectrical characteristic associated with the armored face conveyor,determining a torque associated with the sprocket based on theelectrical characteristic, determining a tension associated with thechain based on the torque, determining an amount of chain stretch basedon the tension, and modifying the position of the hydraulic cylinderbased on the determined amount of chain stretch.

In another implementation, the invention may provide a method ofcontrolling a position of a hydraulic cylinder in an armored faceconveyor. The armored face conveyor includes a sprocket, a chain, achain tension sensor, the hydraulic cylinder, and a controller. Themethod includes measuring or sensing a chain tension using the chaintension sensor, generating a signal related to the sensed chain tension,conditioning the signal related to the sensed chain tension, determiningan amount of chain stretch based on the conditioned signal, andmodifying the position of the hydraulic cylinder based on the determinedamount of chain stretch.

In one embodiment, the invention provides a conveyor for a miningsystem. The conveyor includes a frame, a first sprocket having a firstposition, a second sprocket having a second position, a chain associatedwith the first sprocket and the second sprocket, a sensor configured togenerate a signal related to an electrical characteristic of theconveyor, a drive mechanism coupled to at least one of the firstsprocket and the second sprocket, a hydraulic cylinder, and acontroller. The frame has a fixed first end and an extendable secondend. The first position is separated by a distance from the secondposition. The drive mechanism is configured to drive the at least one ofthe first sprocket and the second sprocket. The controller is configuredto receive the signal from the sensor, determine an amount of chainstretch in the chain based on the received signal, determine a hydrauliccylinder position based on the determined amount of chain stretch, andgenerate a control signal for controlling the hydraulic cylinder to thehydraulic cylinder position.

In another embodiment, the invention provides a method of controlling achain tension for a conveyor in a mining system. The method includesanalyzing a signal associated with the chain tension, determining thechain tension based on the analyzed signal, determining a chainextension based on the determined chain tension, determining a positionfor a hydraulic cylinder based on the determined chain extension, andcontrolling the hydraulic cylinder to the position.

In another embodiment, the invention provides a mining system thatincludes a conveyor, a first sensor, a second sensor, a hydrauliccylinder, and a controller. The first sensor is for sensing a chaintension and is configured to generate a first signal indicative of thechain tension. The second sensor is for sensing an electricalcharacteristic of the conveyor and is configured to generate a secondsignal indicative of the chain tension based on the electricalcharacteristic of the conveyor. The controller is configured to receivethe first signal from the first sensor, receive the second signal fromthe second sensor, determine a chain tension based on one of the firstsignal and the second signal, and control a position of the hydrauliccylinder based on the determined chain tension.

Independent aspects of the invention will become apparent byconsideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an end frame of a chain conveyor.

FIG. 2 illustrates a controller for an AFC according to a constructionof the invention.

FIG. 3 is a diagram illustrating a manner in which chain tension variesalong the length of an AFC.

FIG. 4 is a diagram illustrating a relationship between shearer positionand an amount of mined material loaded on an AFC.

FIG. 5 is a diagram illustrating a relationship between the amount minedmaterial loaded on an AFC and the position of a hydraulic cylinder.

FIG. 6 is a diagram illustrating variations in chain tension withrespect to different locations on a chain.

FIG. 7 is a diagram illustrating the motor power associated with amaingate motor and a tailgate motor of an AFC.

FIG. 8 is a process for controlling a position of a hydraulic cylinder.

FIG. 9 is another process for controlling a position of a hydrauliccylinder.

FIG. 10 is a perspective view of an end frame of a chain conveyor.

FIG. 11 is an enlarged view of the end frame of the chain conveyor ofFIG. 10.

FIG. 12 is a perspective view of a sensor assembly.

FIG. 13 is an assembly view of the sensor assembly shown in FIG. 12.

FIG. 14 is cross-sectional view of the sensor assembly shown in FIG. 12taken along line 15-15.

FIG. 15 is an enlarged cross-sectional view of the sensor assembly shownin FIG. 14.

FIG. 16 is an enlarged cross-sectional view of the sensor assembly shownin FIG. 14.

FIG. 17 is an exploded view of a spring assembly.

FIG. 18 is a cross-sectional view of the sensor assembly shown in FIG.17.

FIG. 19 is an enlarged cross-sectional view of a sensor assembly.

DETAILED DESCRIPTION

Before any independent embodiments of the invention are explained indetail, it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thefollowing drawings. The invention is capable of other independentembodiments and of being practiced or of being carried out in variousways.

Implementations and constructions of the invention described hereinrelate to a longwall chain conveyor system and the control thereof. Thelongwall chain conveyor system includes, for example, armored faceconveyors (“AFCs”) or beam stage loaders (“BSLs”). For descriptivepurposes, the invention is described herein with respect to embodimentsthat include AFCs. AFCs include, for example, a return end frame, afirst sprocket, a second sprocket, one or more chains, one or moremotors, one or more hydraulic cylinders, a controller, and a userinterface. The controller is configured to receive one or more signalsrelated to an electrical characteristic of the AFC and automaticallycontrol the position of the first sprocket or second sprocket based onthe electrical characteristic. The electrical characteristic is, forexample, a voltage, a current, a power factor, motor speed, motortorque, input power, output power, etc. In some implementations, theelectrical characteristic is associated with the one or more motors(e.g., a tailgate motor or a maingate motor) which are used to turn thefirst and second sprocket. Additionally or alternatively, the controlleris configured to receive one or more chain tension signals related to asensed chain tension and automatically control the position of the firstsprocket or second sprocket based on the chain tension signals. Based onthe electrical characteristic or the chain tension signals, thecontroller determines a desired return end frame extension, a desiredposition for the one or more hydraulic cylinders, a desired position forthe first sprocket, a desired position for the second sprocket, anamount of mined material loaded on the AFC, one or more tensionsassociated with the one or more chains, one or more desired tensionsassociated with the one or more chains, a shearer position, etc. Forexample, after the controller has determined a desired position for theone or more hydraulic cylinders, the controller controls the one or morehydraulic cylinders to the desired position to reposition the firstsprocket. In some implementations, the determination of the position forthe one or more hydraulic cylinders is based on a relationship betweenthe electrical characteristic and sprocket torque, chain tension, theamount of mined material loaded on the conveyor, etc.

FIG. 1 illustrates a return end frame 100 that includes, among otherthings, a fixed frame portion, an extendable frame portion, and one ormore hydraulic cylinders. The return end frame 100 is a part of aLongwall mining system that also includes, for example, a shearer. Insome constructions, the position of the extendable frame portion isdetermined using a linear displacement sensor configured to measure theposition of the extendable frame portion through its fullrange-of-motion. The position of the extendable frame portion may bemodified (e.g., incremented or decremented) to correspondingly controlthe position of the one or more hydraulic cylinders, the first sprocket,the second sprocket, etc.

FIG. 2 illustrates a controller 200 associated with the return end frame100. The controller 200 is connected or coupled to a variety ofadditional modules or components, such as a user interface module 205,one or more indicators 210, a power supply module 215, one or moresensors 220, a motor parameters module 225, and the one or morehydraulic cylinders 230. The one or more sensors 220 are, for example,power transducers within the AFC configured to measure or sense anelectrical characteristic (e.g., current, voltage, power factor, torque,speed, input power, output power, etc.), chain tension sensorsconfigured to directly measure or sense chain tension, etc. The use oftransducers that are, in many instances, included in the AFC reduces oreliminates the need for specialty transducers. In some constructions,power transducers and chain tension sensors are both used (e.g., onefunctions as a redundant system for the other). Additionally, the powertransducers are positioned away from hostile areas that may lead todamage or constant replacement of the transducers. The controller 200includes combinations of software and hardware that are operable to,among other things, control the operation of the AFC, control theposition of the return end frame 100, activate the one or moreindicators 210 (e.g., LEDs or a liquid crystal display (“LCD”)), etc.The controller 200 includes, among other things, a processing unit 235(e.g., a microprocessor, a microcontroller, or another suitableprogrammable device), a memory 240, and a bus. The bus connects variouscomponents of the controller 200, including the memory 240, to theprocessing unit 235. In some constructions, the controller 200 is alsoconnected to a communications module that is configured to communicateover one or more networks.

The memory 240 includes, for example, a read-only memory (“ROM”), arandom access memory (“RAM”), an electrically erasable programmableread-only memory (“EEPROM”), a flash memory, a hard disk, an SD card, oranother suitable magnetic, optical, physical, or electronic memorydevice. The processing unit 235 is connected to the memory 240 andexecutes software that is capable of being stored in the RAM (e.g.,during execution), the ROM (e.g., on a generally permanent basis), oranother non-transitory computer readable medium such as another memoryor a disc. Additionally or alternatively, the memory 240 is included inthe processing unit 235. The controller 200 also includes aninput/output (“I/O”) system 245 that includes routines for transferringinformation between components within the controller 200 and othercomponents of the AFC. Software included in the implementation of theAFC is stored in the memory 240 of the controller 200. The softwareincludes, for example, firmware, one or more applications, program data,one or more program modules, and other executable instructions. Thecontroller 200 is configured to retrieve from memory and execute, amongother things, instructions related to the control processes and methodsdescribed herein. In other constructions, the controller 200 includesadditional, fewer, or different components. The power supply module 215supplies a nominal AC or DC voltage to the AFC and the components andmodules within the AFC. For example, the power supply module 215 ispowered by an approved mine power supply.

The motor parameters module 225 is connected to or associated with oneor more motors or drive mechanisms that are coupled to the firstsprocket and/or the second sprocket. The motor parameters module 225 isconnected to or included in, for example, one or more switchgears. Themotor parameters module 225 is configured to receive signals associatedwith one or more parameters (e.g., current, voltage, power factor,torque, speed, input power, output power, etc.) of one or more motors.In some embodiments, the motor parameters module 225 receives signalsrelated to the motor parameters. In other embodiments, the motorparameters module 225 includes or is connected to the one or moresensors 220 for sensing the motor parameters. The motors are controlledby control signals received from the controller 200 or anotherassociated controller, such as a switchgear. The one or more motors arealso coupled to gear reduction boxes to reduce the rotational speed ofthe motor to a rotational speed appropriate for the sprockets andconveyor. In some implementations, the controller 200 is configured tocontrol the motors and the AFC autonomously using a plurality of sensorsand one or more stored programs or modules. In other implementations,the controller 200 is configured to control the motors and the AFC basedon a combination of manual inputs and automatic controls. The one ormore hydraulic cylinders 230 also receive control signals from thecontroller 200, and selectively extend the return end frame (e.g.,change the position of the one or more hydraulic cylinders, the firstsprocket, the second sprocket, etc.) based on the control signals fromthe controller 200. The controller 200 also monitors the one or moremotors and the one or more hydraulic cylinders 230 to determine relatedcharacteristics. For example, the controller 200 can monitor or senseelectrical characteristics of the one or more motors, the position ofthe one or more hydraulic cylinders 230 (e.g., an extension of the oneor more hydraulic cylinders), etc. Although a single controller isillustrated, in other constructions, the controller 200 may be separatedinto a plurality of controllers. For example, the controller 200 may beseparated into a consolidated control unit (“CCU”), a programmablecontrol unit (“PCU”), one or more switchgears, etc. The CCU can behoused in an explosion-proof enclosure and provides control over thelongwall conveyor system. The PCU is an intrinsically safe system thatcan be interfaced with the CCU for, among other things, stopping,inhibiting, tripping, etc., the operation of the conveyor. The one ormore switchgears are configured to control the starting and stopping ofthe conveyor, provide protection to the one or more motors, sense ormonitor one or more parameters (e.g., electrical parameters) of the oneor more motors, etc. Signals from the one or more switchgears andassociated with the one or more motor parameters can then be providedto, for example, the CCU, the controller 200, the motor parametersmodule 225, etc.

The user interface module 205 is used to control or monitor the AFC orthe Longwall mining system. For example, the user interface module 205is operably coupled to the controller 200 to control the speed of theconveyor, the speed of the one or more motors, etc. The user interfacemodule 205 can include a combination of digital and analog input oroutput devices required to achieve a desired level of control andmonitoring for the AFC. For example, the user interface module 205 caninclude a display and input devices such as a touch-screen display, oneor more knobs, dials, switches, buttons, etc. The display is, forexample, a liquid crystal display (“LCD”), a light-emitting diode(“LED”) display, an organic LED (“OLED”) display, an electroluminescentdisplay (“ELD”), a surface-conduction electron-emitter display (“SED”),a field emission display (“FED”), a thin-film transistor (“TFT”) LCD,etc. In other constructions, the display is a Super active-matrix OLED(“AMOLED”) display. The user interface module 205 can also be configuredto display conditions or data associated with the AFC in real-time orsubstantially real-time. For example, the user interface module 205 isconfigured to display measured electrical characteristics of the AFC,the status of the AFC, chain tensions, fault conditions (e.g., slackchain, zero tension chain, etc.), an amount of mined material on theconveyor, etc. In some implementations, the user interface module 205 iscontrolled in conjunction with the one or more indicators 210 (e.g.,LEDs) to provide visual indications of the status or conditions of theAFC.

In some embodiments, the information and data associated with theoperation of the AFC is sent, transferred, or transmitted to a remote ormobile device for remote monitoring, remote control, data logging, etc.The remote or mobile device is, for example, a personal computer, alaptop computer, a mobile phone, a tablet computer, a personal digitalassistant (“PDA”), an e-reader, a server, a database, etc. In someimplementations, the data is transferred via a wireless local areanetwork (“LAN”), a neighborhood area network (“NAN”), a home areanetwork (“HAN”), or a personal area network (“PAN”) using any of avariety of communications protocols, such as Wi-Fi, Bluetooth, ZigBee,etc. Additionally or alternatively, the data is transferred to theremote or mobile device over a wide area network (“WAN”) (e.g., a TCP/IPbased network, a Global System for Mobile Communications (“GSM”)network, a General Packet Radio Service (“GPRS”) network, a CodeDivision Multiple Access (“CDMA”) network, an Evolution-Data Optimized(“EV-DO”) network, an Enhanced Data Rates for GSM Evolution (“EDGE”)network, a 3GSM network, a Digital Enhanced Cordless Telecommunications(“DECT”) network, a Digital AMPS (“IS-136/TDMA”) network, an IntegratedDigital Enhanced Network (“iDEN”) network, a Digital Advanced MobilePhone System (“D-AMPS”) network, etc.).

The remote or mobile device includes, for example, a separatecontroller, a user interface module, a display, a power supply module,and a communications module which operates in a similar manner tocorresponding components of the AFC described above. The remote ormobile device also includes, for example, combinations of software andhardware that are operable to, among other things, control the operationof the AFC, control the information that is presented on the display,etc. The information received from the AFC can be received through thecommunications module which includes one or more antennas, one or morenetwork interface cards (“NICs”), etc., for communicating over one ormore of the networks described above.

As previously indicated, in some implementations, the controller 200 isconfigured to prevent a zero tension or slack chain condition in the oneor more chains by using an electrical characteristic associated with theAFC to automatically control the position of the one or more hydrauliccylinders. The controller 200 is also configured to receive signals fromthe one or more sensors 220 associated with the one or more motors, theone or more hydraulic cylinders 230, one or more chains, or othercomponents of the AFC. The signals from the sensors 220 are related to,for example, tensions of one or more chains or the voltage, the current,the power factor, the motor speed, the motor torque, the input power,the output power, etc., of the one or more motors. The controller 200then processes and analyzes the signals to determine a desired hydrauliccylinder position that is based on an amount of chain stretch. Theamount of chain stretch is dependent upon, among other things, an amountof mined material loaded on the conveyor. In some implementations, thetotal electrical power of the AFC is used to control the position of thehydraulic cylinder. In other implementations, the power of one of theone or more motors (e.g., a maingate motor or a tailgate motor) is usedto control the position of the hydraulic cylinder.

In some implementations, the controller 200 controls the position of thehydraulic cylinder based on one or more relationships between theelectrical characteristic (e.g., power) of the AFC and a position of theone or more hydraulic cylinders 230, a position of the first or secondsprocket, a tension of the one or more chains, an amount of minedmaterial loaded on the conveyor, a shearer position, etc. Depending onthe electrical characteristic, the one or more hydraulic cylinders 230are controlled to increase or decrease the distance between the firstsprocket and the second sprocket to account for the stretching of theone or more chains that occurs when the mined material is loaded on theconveyor. By automatically controlling the position of the hydrauliccylinder based on the electrical characteristic during operation of theAFC, the amount of pre-tensioning required can be significantly reduced,which reduces the amount of strain and wear on the one or more chains,the sprockets, etc. In other implementations, the controller 200controls the position of the hydraulic cylinder in a similar mannerbased on the sensed tensions of one or more chains. Additionally,automatically controlling the position of the hydraulic cylinder, asdescribed, allows the controller 200 to implement a variety ofmechanisms for improving operation of the AFC. For example, thecontroller 200 can shut down the AFC in the event of a loss of chaintension, loss of hydraulic pressure, unplanned change in the position ofthe hydraulic cylinder, when the position of the hydraulic cylinder issupposed to have been modified but no modification was detected, etc.

In some implementations, both the chain tension and the electricalcharacteristic are sensed. For example, the chain tension is directlymeasured with a first or chain tension sensor, and the electricalcharacteristic is measured with a second sensor, such as a powertransducer. In such an implementation, a first signal generated by thefirst sensor and a second signal generated by the second sensor are bothreceived by the controller 200, and one signal is a back-up of the othersignal. For example, when the first signal is not received, thecontroller 200 uses the second signal to determine chain tension.Alternatively, when the second signal is not received, the controller200 uses the first signal to determine chain tension. In someimplementations, the first signal and the second signal can be comparedto one another to determine whether one of the first sensor or secondsensor is in a fault condition. During a fault condition, the controller200 may not receive a signal from one (or both) of the first sensor andthe second sensor. For example, if the first sensor is the primarysensor, but the controller 200 does not receive a signal from the firstsensor (or the signal is corrupt), the controller uses the signal fromthe second sensor to determine chain tension. Alternatively, if thesecond sensor is the primary sensor, but the controller 200 does notreceive a signal from the second sensor (or the signal is corrupt), thecontroller 200 uses the signal from the first sensor to determine chaintension. In some implementations, both the first and the second signalsare used to determine chain tension.

FIGS. 3-7 illustrate various relationships associated with the operationof the AFC or a Longwall mining system based on test data. Although oneor more of the diagrams associated with FIGS. 4-7 may be combined into asingle diagram, the diagrams are shown separately for illustrativepurposes. As such, one or more of the diagrams may illustrate arelationship between, for example, mined material loaded on a conveyorand the position of a hydraulic cylinder, but may be shown with respectto another characteristic of a Longwall mining system (e.g., shearerposition). Such relationships are illustrative of the variouscorrespondences among and dependencies of the described characteristicsof Longwall mining systems. Additionally, each of the diagrams isillustrated with time (i.e., minutes) along an x-axis of a coordinatesystem. By uniformly illustrating time among the diagrams, therelationships between the characteristics and components of the Longwallmining system may be more easily distinguished.

FIG. 3 illustrates a conveyor 300 that includes a first sprocket 305(e.g., a return end tailgate sprocket) and a second sprocket 310 (e.g.,a delivery end maingate sprocket). The first and second sprockets 305and 310 are spaced apart from one another and connected by a chain 315that is wrapped around both the first sprocket 305 and the secondsprocket 310. The tension of the chain 315 is represented by the line320. The further the line 320 is from the chain 315, the greater thetension in the chain 315. As shown in FIG. 3, the tension variesthroughout the length of the chain 315 and is the greatest at the bottomportion 325 of the first sprocket 305 (i.e., the tailgate sprocket) andthe top portion 330 of the second sprocket 310 (i.e., the maingatesprocket). The tensions associated with conveyor 300 are furtherdescribed and illustrated graphically below with respect to FIG. 6.

FIG. 4 is a diagram 400 that illustrates a relationship between shearerposition (i.e., a shearer of a Longwall mining system) and the amount ofmined material loaded on the AFC (i.e., in tons per meter [“t/m”]). Theshearer position is depicted with respect to a percentage (%) of thewall surface. For example, if the shearer is located at an extreme farend of a Longwall mining system, the percentage of the shearer'sposition is 100% (i.e., with respect to the full range of motion of theshearer along the wall face). As the shearer position increases, theamount of mined material that is loaded on the AFC also increases inrelation to the shearer position.

FIG. 5 is a diagram 500 of a relationship between the amount of minedmaterial loaded on the conveyor 300 (i.e., in t/m) and the position ofthe hydraulic cylinder (i.e., in meters [“m”]). The relationshipillustrated in diagram 500 is illustrated with respect to the shearerposition previously illustrated and described with respect to FIG. 4. Asthe shearer position increases, the amount of mined material loaded onthe conveyor 300 correspondingly increases. The increased amount ofmined material increases the amount of stretch in the chain 315. As thechain is stretched, the sprocket must be pushed out to take in the slackcaused by the stretching of the chain and to ensure proper operation andreliability of the AFC.

FIG. 6 is a diagram 600 of the tensions (i.e., in tons) at variouslocations of the chain 315. For example, the diagram 600 includes thetop maingate tension, the top tailgate tension, the bottom maingatetension, and the bottom tailgate tension. The tensions are given in tonsand are also related to the position of the shearer, the amount of minedmaterial loaded on the conveyor 300, and the position of the hydrauliccylinder by comparison to previous FIGS. 4 and 5. With comparison toFIGS. 4 and 5, as the amount of mined material loaded on the conveyor300 increases, the tension in the chain 315 increases. Similarly, as theposition of the shearer increases, the tension in the chain increases.Also, as the tension increases, the hydraulic cylinder is pushed out totake in the slack associated with the stretching of the chain 315.

FIG. 7 is a diagram 700 of the motor power (i.e., in kilowatts [“kW”])for each of the one or more motors (e.g., tailgate motor associated witha first sprocket 305 and a maingate motor associated with a secondsprocket 310). Due to the precision of the power sharing between the twomotors, the differences between the powers used by each motor isvirtually indistinguishable. With continued reference to diagrams 400,500, and 600 above, the power of the maingate and tailgate motors isrelated to the shearer position, the chain tension, the amount of minedmaterial loaded on the conveyor 300, and the position of the hydrauliccylinder. As such, the controller 200 is able to use these relationshipsto control the operation of the AFC based on motor power, anotherelectrical characteristic of the AFC, a sensed chain tension, etc. Forexample, the relationships between one or more electricalcharacteristics of the maingate and tailgate motors are stored in memory(e.g., the memory 240). The relationships can be stored as one or morefunctions, one or more look up tables (“LUTs”), or as a series ofthresholds to which the motor power or another characteristic of the AFCcan be compared.

In some implementations, an electrical characteristic value is used tocontrol the position of the hydraulic cylinder and thus the tension ofthe chain 315 (e.g., the tailgate top tension). The position ofhydraulic cylinder is related (e.g., proportional) to the differencebetween the electrical characteristic value and a corresponding no-loadelectrical characteristic value. The difference between the measuredelectrical characteristic value and the no-load electricalcharacteristic value can then be used to determine a torque associatedwith one or more of the first sprocket 305 and second sprocket 310. Thesprocket torque is used in conjunction with a known stiffness of thechain 315 and a characteristic stretching of the chain 315 to determinea distance that the hydraulic cylinder is to be extended. The positionof the hydraulic cylinder (e.g., the extension of the hydrauliccylinder) is then modified to account for the stretch in the chain 315.As previously described, modifying the position of the hydrauliccylinder modifies the relative positions of the first sprocket 305 andthe second sprocket 310.

In constructions that include a chain tension sensor, a chain tensionsignal generated by the chain tension sensor can be used to control theposition of the hydraulic cylinder. The chain tension sensor isconfigured to directly measure the tension of one or more chains. Anexample of a system including a chain tension sensor is described andillustrated in Appendix A. The chain tension signal is, for example, alow-voltage signal that is indicative of the amount of tensionassociated with one or more chains. The controller 200 receives thechain tension signal. A signal conditioner or signal conditioning modulewithin the controller 200 is configured to analyze and/or condition thelow-voltage chain tension signal by identifying and sampling one or moresignal peaks, averaging the sampled signal peaks, and generating aconditioned signal indicative of the dynamic tension of the one or morechains (e.g., in units of tons-per-chain). The controller is alsoconfigured to display the dynamic tension to a user, display diagnosticsof the chain tension sensor to the user, calibrate the chain tensionsensor, etc. The sensed chain tension (e.g., the conditioned signalindicative of the dynamic tension of one or more chains) can then beused in conjunction with a known stiffness of the chain 315 and acharacteristic stretching of the chain 315 to determine a distance thatthe hydraulic cylinder is to be extended. The position of the hydrauliccylinder (e.g., the extension of the hydraulic cylinder) is thenmodified to account for the stretch in the chain 315. As previouslydescribed, modifying the position of the hydraulic cylinder modifies therelative positions of the first sprocket 305 and the second sprocket310.

With respect to implementations of the invention in which a LUT is used,values for cylinder position, sprocket position, chain stretch, etc.,are stored in memory corresponding to a plurality of electricalcharacteristic values or sensed chain tension values. In someimplementations, 8-bit numbers (i.e., 256 values) or 16-bit numbers(i.e., 65,536 values) are used to identify a sprocket position, a chaintension, or a cylinder position that corresponds to the electricalcharacteristic value or the sensed chain tension value. The electricalcharacteristic value or chain tension value is used as an input valuethat is compared to the values stored in the LUT. The LUT entry thatcorresponds to the input value is then retrieved by the controller 200,and the position of the hydraulic cylinder, the sprocket position, etc.is adjusted accordingly. With respect to embodiments of the inventionthat use one or more functions (e.g., stored in memory 240), theelectrical characteristic value or chain tension value is used as aninput value to the one or more functions such that the controller 200 isable to calculate a corresponding hydraulic cylinder position, sprocketposition, etc. Such a calculation technique may allow for finer controlof the hydraulic cylinder position than using a LUT. With respect toimplementations of the invention that use a variety of threshold values,the electrical characteristic value or chain tension value is comparedsequentially to a series of threshold values. The threshold valuescorrespond to the hydraulic cylinder position, the chain tension, thesprocket position, etc. In some implementations of the invention, thecomparisons to threshold values are used when coarse hydraulic positioncontrol, chain tension control, sprocket position control, etc., isacceptable.

FIG. 8 is a process 800 for controlling the AFC. At step 805, a valuefor an electrical characteristic is determined (e.g., measured, sensed,calculated, etc.). As described above, the electrical characteristic is,for example, a voltage, a current, a power factor, motor speed, motortorque, input power, output power, etc. Using the electricalcharacteristic value, the controller 200 is configured to determine asprocket torque (step 810). As an illustrative example, the sprockettorque can be determined based on a power value of a motor and arotational speed of a sprocket. Using these values, the torque can becalculated. A chain tension can then be calculated based on the sprockettorque (step 815). As previously described, the tension of the chain isrelated to an amount of stretch in the chain. Using the storedrelationship (e.g., in memory 240) between chain tension and chainstretch, the amount of extension of the chain can be determined (step820). The amount of chain extension is then associated (e.g., directlyor indirectly) with a desired position of the hydraulic cylinder or adesired change in position of the hydraulic cylinder (step 825). Basedon the desired position or change in position of the hydraulic cylinder,the controller 200 generates one or more control signals to control thehydraulic cylinder to the new position (step 830). Although the process800 is described above with respect to controlling the position of ahydraulic cylinder, the process 800 an similarly be executed withrespect to different characteristics of the AFC or a Longwall miningsystem, such as sprocket position, chain tension, shearer position, theamount of coal loaded on the AFC, the position of the extendable portionof the frame 100, etc.

FIG. 9 illustrates a process 900 for controlling the AFC. At step 905,chain tension is sensed using the chain tension sensor. The chaintension sensor generates a signal (step 910) that is indicative of thesensed chain tension. The chain tension signal is received by thecontroller 200 where a signal conditioning module conditions the chaintension signal (step 915) (e.g., samples, averages, etc.). Theconditioned chain tension signal is then used to identify or determinethe sensed tension in one or more chains (step 920). For example, theconditioned chain tension signal may correspond to an averaged voltagevalue from the chain tension sensor. A relationship between the averagedvoltage and chain tension is then used to determine the actualcorresponding chain tension. As previously described, the tension of thechain is related to an amount of stretch in the chain. Using the storedrelationship (e.g., in memory 240) between chain tension and chainstretch, the amount of extension of the chain can be determined (step925). The amount of chain extension is then associated (e.g., directlyor indirectly) with a desired position of the hydraulic cylinder or adesired change in position of the hydraulic cylinder (step 930). Basedon the desired position or change in position of the hydraulic cylinder,the controller 200 generates one or more control signals to control thehydraulic cylinder to the new position (step 935). Although the process900 is described above with respect to controlling the position of ahydraulic cylinder, the process 900 can similarly be executed withrespect to different characteristics of the AFC or a Longwall miningsystem, such as sprocket position, chain tension, shearer position, theamount of coal loaded on the AFC, the position of the extendable portionof the frame 100, etc.

FIGS. 10-11 illustrate a portion of a longwall conveyor 1022 including areturn end 1026 (FIG. 11), a conveying element or chain 1014 thattravels between the return end 1026 and a delivery end (not shown), andthe sensor assembly 1010 proximate the return end 1026. The return end1026 includes a frame 1038, an idler or take-up shaft 1042 mounted onthe frame 1038, and at least one hydraulic actuator (not shown). Theframe 1038 moves with respect to the delivery end, between an innerretracted position and an outer extended position through the extensionand retraction of the hydraulic actuator. The chain 1014 passes aroundthe take-up shaft 1042 to travel in a continuous loop between thedelivery end and the return end 1026. The chain 1014 includes aplurality of flight members 1050 mounted on the chain 1014 and spacedapart by a first distance in a direction of travel 1054 of the chain1014.

As shown in FIGS. 12-15, the sensor assembly 1010 is positioned adjacenta wear strip 1062 of a flange portion 1066 of the frame 1038 andincludes a reaction arm 1070, a main support hinge pin 1074, a reactionbracket 1078 (FIGS. 13-14), a load sensing pin 1082 (FIGS. 13-14), and aspring assembly 1086. Examples of sensor assemblies can also be found inU.S. patent application Ser. No. 13/297,067, entitled “CHAIN TENSIONSENSOR” and filed on Nov. 15, 2011, and U.S. patent application Ser. No.______, (Attorney Docket No. 051077-9175-US02), entitled “CHAIN TENSIONSENSOR” and filed on Jul. 19, 2012, the entire contents of both of whichare hereby incorporated by reference.

Another example of a sensor assembly is disclosed in U.S. Pat. No.8,061,510, entitled “DUAL SENSOR CHAIN BREAK DETECTOR,” which issued onNov. 22, 2011, and the entire content of which is hereby incorporated byreference.

The reaction arm 1070 has a first end 1090, a shoulder 1094, a secondend 1098 (FIG. 13), and a load pad 1102. The first end 1090 is rotatablycoupled to a secondary support plate 1106 of the frame 1038 by the mainsupport hinge pin 1074. The shoulder 1094 is positioned proximate thefirst end 1090. The second end 1098 includes a hole 1122 (FIGS. 13 and14) extending from the second end 1098 partially through the reactionarm 1070 in a longitudinal direction. The load pad 1102 is positionedintermediate the first end 1090 and the second end 1098. As shown inFIG. 11, the load pad 1102 is positioned parallel to the wear strip 1062to contact the flight members 1050 passing the wear strip 1062, causingthe reaction arm 1070 to rotate about the hinge pin 1074. The load pad1102 also provides a continuous guide surface to guide the flightmembers 1050 as the flight members 1050 travel around the take-up shaft1042.

The hinge pin 1074 is mounted to the secondary support plate 1106 of theframe 1038 and is positioned substantially transverse to the directionof travel 1054 of the chain 1014. The hinge pin 1074 restricts themotion of the reaction arm 1070 in every direction except rotation (seearrow 1130) about the hinge pin 1074.

As shown in FIGS. 13-15, the reaction bracket 1078 is mounted to thesecondary support plate 1106 of the frame 1038 and includes a slot 1138.The reaction bracket 1078 is configured to fit within the second end1098 of the reaction arm 1070 such that the slot 1138 is aligned withthe hole 1122 extending through the reaction arm 1070. The load sensingpin 1082 is positioned in the slot 1138 of the reaction bracket 1078 andwithin the hole 1122 of the reaction arm 1070. The load sensing pin 1082is therefore positioned substantially perpendicular to the hinge pin1074. The load sensing pin 1082 is attached to a sensing cable 1150(FIGS. 14 and 15).

As shown in FIG. 16, the shoulder 1094 includes a head side 1162, aspring side 1166, and a bore 1168 extending between the head side 1162and the spring side 1166 through the reaction arm 1070 in a directiontangential to a direction of rotation 1130 of the reaction arm 1070(i.e., perpendicular to the hinge pin 1074). Referring to FIGS. 16 and17, the spring assembly 1086 includes a pin or bolt 1170, a nut 1172, aplurality of spring washers 1174, and a retaining washer 1178. The bolt1170 is coupled to the wear strip 1062 and passes through the shoulderbore 1168. The bolt 1170 includes a smooth portion 1180, a shoulder1182, and a threaded portion 1184 for threadingly engaging the nut 1172,which is tightened to secure the shoulder 1094 with respect to the bolt1170.

The spring washers 1174 are positioned around the bolt 1170 adjacent thespring side 1166, between the shoulder 1094 and the wear strip 1062. Inthe embodiment shown in FIG. 18, the bolt 1170 includes a cavity recess1186 to reduce the material contact between the wear strip 1062 and thebolt 1170, thereby reducing the amount of heat transfer from the wearstrip 1062 to the bolt 1170. The retaining washer 1178 is positionedbetween the spring side 1166 of the shoulder 1094 and the spring washers1174. The retaining washer 1178 is screwed onto the bolt 1170 past thethreaded portion 1184 of the bolt 1170, effectively “capturing” thespring washers 1174 around the smooth portion 1180. Each spring washer1174 has a generally frusto-conical shape that creates a spring force asthe spring washer 1174 is compressed. The compression of the springwashers 1174 therefore applies a pre-loaded force to the reaction arm1070, biasing the reaction arm 1070 away from the frame 1038. Theretaining washer 1178 centers the top-most spring washers 1174 withrespect to the bolt 1170.

In the embodiment shown in FIG. 16, the nut 1172 is capped in order toprevent the nut 1172 from being tightened against the shoulder 1094.This maintains a clearance between the nut 1172 and the reaction arm1070, allowing the pre-load force of the spring washers 1174 to beapplied on the load pin 1082. In another embodiment (see FIGS. 17-19),the nut 1172 is open allowing the nut 1172 to be tightened against theshoulder 1094 (FIG. 19). As the nut 1172 is tightened, the retainingwasher 1178 compresses each spring washer 1174, and the reaction armshoulder 1094 is secured against the retaining washer 1178. Tighteningthe nut 1172 causes the retaining washer 1178 to draw closer to the boltshoulder 1182 (FIG. 18). Once the retaining washer 1178 contacts thebolt shoulder 1182, the nut 1172 cannot be tightened any further. Inthis way, the bolt shoulder 1182 provides mechanical lock-out,preventing over-compression of the spring washers 1174.

The spring washers 1174 may be stacked in a number of configurations inorder to obtain the desired pre-load force on the reaction arm 1070. Forinstance, the spring washers 1174 may be stacked in alternating setssuch that the “peaks” of two washers 1174 are against each other, andthe “peaks” of the adjacent washers 1174 are inverted with respect tothe first two (see FIG. 18). The desired configuration can beaccomplished using fewer or more washers 1174 in each set.Alternatively, all of the washers 1174 can be aligned in one direction.In another alternative, a single spring washer 1174 may be used. Instill other constructions, a different type or shape of spring may beused.

A plurality of shims 1190 (see FIG. 19) may be added to the area betweenthe retaining washer 1178 and the cavity recess 1186 in order to accountfor the build-up of tolerances in the bolted joint and/or to applyadditional compressive force on the spring washer(s) 1174.

During operation, the load pad 1102 of the reaction arm 1070 contactsthe flight members 1050 of the chain 1014 as the flight members 1050pass between the return end 1026 and the delivery end. In this manner,the load pad 1102 is subjected to the vertical component of the chaintension. Contact with the flight members 1050 causes the reaction arm1070 to rotate about the hinge pin 1074.

Referring to FIG. 14, as the reaction arm 1070 rotates in the directionof rotation 1130, the second end 1098 deflects upwardly, exerting anupward force on the load sensing pin 1082. The reaction bracket 1078resists this deflection, exerting a downward force on the load sensingpin 1082, thereby creating a shear load condition on the pin 1082. Theload sensing pin 1082 senses the magnitude of the shear force and/or thestrain and transmits a signal indicative of the force or strain throughthe sensing cable 1150 to a chain controller (not shown). The chaincontroller then uses this information to determine the tension in thechain 1014 and to calculate the necessary change in position of thereturn end frame 1026 in order to maintain the desired tension in thechain 1014.

The biasing force of the spring assembly 1086 provides a pre-load forcethat can be calibrated. Instead of calibrating the tension to themaximum load the chain 1014 may experience during operation (e.g., inone embodiment, approximately five tons; in other embodiments, thismaximum load may be greater than or less than this value), the positivepre-load permits the chain tension to be set to a lesser load. This mayreduce inter-link chain wear and sprocket wear and, ultimately, increasethe life of the chain 1014. In addition, the tolerance “stack-up” of thespring washers 1174 provides a wide range of configurations and pre-loadcharacteristics for the reaction arm 1070. In one example, a pre-load inthe range of 200 to 400 lbs. may provide improved results for even veryhigh material loads.

In one embodiment, the pre-load acts on the reaction arm 1070 in a“positive” direction (i.e., substantially parallel to the direction ofthe force exerted on the reaction arm 1070 by the flight members 1050).The positive base load may facilitate accurate measurement in straingauge sensors, enhancing accuracy of the system. In addition, thepositive pre-load may also reduce the occurrence of negative outputs,which can falsely trigger system alerts.

Due to the perpendicular orientation of the load sensing pin 1082 withrespect to the hinge pin 1074, the load sensing pin 1082 only senses thevertical component (e.g., the rotation of the reaction arm 1070 aboutthe hinge pin 1074) of the force exerted on the reaction arm 1070. Thiseffectively isolates the load sensing pin 1082 from impacts to the loadpad 1102 of the reaction arm 1070, resulting in improved reliability anda more accurate electrical signal.

Also, in one embodiment, the load pad 1102 has a length that is asignificant proportion of the distance between the flight members 1050.In one embodiment, the load pad 1102 has a length in a range betweenapproximately 60% and approximately 70% of the distance between theflight members 1050. This significant length provides a smaller gapbetween the moment when one flight member 1050 contacts the load pad1102 and the moment when a second flight member 1050 contacts the loadpad 1102, reducing the oscillation of the load pad 1102 (and thereforethe load sensing pin 1082) between a loaded position and an unloadedposition. This aids the load sensing pin 1082 in generating a smooth,level signal.

Spurious loading arising from the impact of the flight members 1050 withthe load pad 1102 is absorbed by the main support hinge pin 1074, whichis positioned at a right angle to both the direction of travel 1054 ofthe chain 1014 and the flight members 1050. In addition, the loadsensing pin 1082 is not directly in contact with the wear strip 1062,reducing the impact loading and insulating the load sensing pin 1082from heat caused by the friction contact of the flight members 1050sliding against the underside of the wear strip 1062.

In an alternative independent embodiment, the conveyor 1022 may includea plurality of load sensor assemblies 1010. For example, the conveyor1022 may include a sensor assembly 1010 mounted on each side of thechain 1014, with each sensor 1010 measuring the tension in theassociated chain 1014 independently and permitting the operator todetect breakage in either chain 1014. Because the chains 1014 areconnected to one another by the flight members 1050, some amount of thetension load in the chains 1014 will be shared in the event that a chain1014 breaks.

While the described location of the sensor assembly 1010 is beneficialbecause the sensor assembly 1010 is subjected to less direct impactloads, in an alternative embodiment, the sensor assemblies 1010 may bespaced along the length of and on either side of the conveyor 1022.

Thus, the invention may generally provide, among other things, systemsand methods for controlling the operation of a mining system based on anelectrical characteristic and/or a tension sensor.

What is claimed is:
 1. A conveyor for a mining system, the conveyorcomprising: a frame having a fixed first end and an extendable secondend; a first sprocket having a first position; a second sprocket havinga second position, the first position being separated by a distance fromthe second position; a chain associated with the first sprocket and thesecond sprocket; a sensor configured to generate a signal related to anelectrical characteristic of the conveyor; a drive mechanism coupled toat least one of the first sprocket and the second sprocket, the drivemechanism being configured to drive the at least one of the firstsprocket and the second sprocket; a hydraulic cylinder; and a controllerconfigured to receive the signal from the sensor, determine an amount ofchain stretch in the chain based on the received signal, determine ahydraulic cylinder position based on the determined amount of chainstretch, and generate a control signal for controlling the hydrauliccylinder to the hydraulic cylinder position.
 2. The conveyor of claim 1,wherein the electrical characteristic includes a voltage, a current, apower factor, a motor speed, a motor torque, a motor input power, or amotor output power.
 3. The conveyor of claim 1, wherein the amount ofchain stretch is related to an amount of mined material loaded on theconveyor.
 4. The conveyor of claim 1, wherein the hydraulic cylinderposition controls the distance between first sprocket and secondsprocket.
 5. The conveyor of claim 1, wherein the sensor is a powertransducer.
 6. The conveyor of claim 1, wherein the drive mechanismincludes a motor.
 7. The conveyor of claim 1, wherein the controller isfurther configured to determine a third position for the second sprocketbased on the determined amount of chain stretch.
 8. A method ofcontrolling a chain tension for a conveyor in a mining system, themethod comprising: analyzing a signal associated with the chain tension;determining the chain tension based on the analyzed signal; determininga chain extension based on the determined chain tension; determining aposition for a hydraulic cylinder based on the determined chainextension; and controlling the hydraulic cylinder to the position. 9.The method of claim 8, wherein the signal is generated by a powertransducer.
 10. The method of claim 8, wherein the signal is generatedby a chain tension load sensor.
 11. The method of claim 10, wherein thechain tension load sensor includes a load sensing pin.
 12. The method ofclaim 11, wherein the load sensing pin is configured to sense amagnitude of a shear force.
 13. The method of claim 8, whereincontrolling the hydraulic cylinder to the position controls a distancebetween a first sprocket and a second sprocket.
 14. A mining systemcomprising: a conveyor; a first sensor for sensing a chain tension, thefirst sensor being configured to generate a first signal indicative ofthe chain tension; a second sensor for sensing an electricalcharacteristic of the conveyor, the second sensor being configured togenerate a second signal indicative of the chain tension based on theelectrical characteristic of the conveyor; a hydraulic cylinder; and acontroller configured to receive the first signal from the first sensor;receive the second signal from the second sensor; determine a chaintension based on one of the first signal and the second signal; andcontrol a position of the hydraulic cylinder based on the determinedchain tension.
 15. The system of claim 14, wherein the controller isfurther configured to determine the chain tension based on each of thefirst signal and the second signal.
 16. The system of claim 14, whereinthe second signal is related to at least one of a voltage, a current, apower factor, a motor speed, a motor torque, an input power, or anoutput power.
 17. The system of claim 14, wherein the first sensor is achain tension load sensor.
 18. The system of claim 17, wherein the chaintension load sensor includes a load sensing pin.
 19. The system of claim18, wherein the load sensing pin is configured to sense a magnitude of ashear force.
 20. The system of claim 14, wherein the other of the firstsignal and second signal is used to determine chain tension when the oneof the first signal and the second signal is not received by thecontroller.